There are 17 types of symmetry which can used to cover a 2 dimensional surface.
Here are some websites that discuss this.
Detailed discussion of computer generated Zelij patterns:
http://www.mi.sanu.ac.yu/vismath/kaplan/index.html
The basic table of symmetries:
http://www2.spsu.edu/math/tile/symm/ident17.htm
From the same website – an example of a pattern from the Al Hambra with p6m symmetry:
http://www2.spsu.edu/math/tile/grammar/moor/moor3f.htm
The Wikipedia page on rotational symmetry
http://en.wikipedia.org/wiki/Symmetry_combinations
82 Zelij pics on Flickr. I must add mine…
http://www.flickr.com/photos/tags/zelij/interesting/
Dutch artist MC Escher was a master of tiling symmetries
Douglas Hofstadter, ‘Visions of Symmetry’
Tile Generator (design your own replicating tile structure):
http://escher.epfl.ch/escher/
Dr Heinrich Heesch identified 28 types of repeating structure
http://www.eschertile.com/tile28.htm
Tags: 17-fold symmetry, Zelij
